Hello,
after some experiments with a noname VS1053B module I'm going to plan a VS1053B subsystem on my main circuit for my projects (music player for kids with RFID tags, based on a STM32F103xxx MCU) and I have two simple questions:
1. Line In: I need only a stereo line in plug: On the VS1053B datasheet page 14 (circuit diagram) it's well drawn, but what should I do with the "MICN" line? To GND or leave it floating?
2. Are the VS1053B chips sold in china (eg. Aliexpress) fakes or not? They aren't really super cheap so I would guardedly say that they are not counterfeit products. I plan about 10 to 50 prototypes and caused by the madness of globalization it's *much* cheaper for me (Europe-Austria) ordering them from Asia than on regular way in Europe.. But: If there is a reasonable suspicion of counterfeit VS-chips, I'm not going to buy them.
Example: https://www.aliexpress.com/item/VS1053- ... 26442.html

Wow, thank you both for the super fast reply!
Ok, so I'm going to make a test order about 10 chips (I think the chinese sellers buy 100000+ for cheap and sell them with lower margin than european sellers (ok, 15-20 USD for a single chip <100pcs isn't really a reason to buy). Strange way the conditions of chinese products are mostly good (I'm a ali diamond member) if you can wait a long time. Side note: Every lost or damaged parcel was caused by Austrian Post.... (4-5 from 1000+ the last years)
Anyway: I like the 1053B and I'm really happy to experiment with it (I was considering using a STM32F4xxx and doing the audio part native with I2S, but the VS chip is much easier to handle (no need for generate negative voltage and a very simple circuit) and more versatile for future ideas)

The ideas are open end... I like this.
I'm going to produce about 10 devices for friendly families (and one for my younger daughter) . This is my first test phase, so I can modify the hardware and firmware if there are faults easily ("Bring your player and some beers, you'll get fancy new features!").
The player, even if I'm going to produce many of them (I don't know my future) will be and stay open hardware and open source.
Even a "music player" can be a real big project, as I know for now... The idea behind that started more than 3 years ago, as I developed a first player for my older daughter. The main reason was dissatisfaction with all music players for kids on the market: Too much plastic, too fragile, too much unnecessary functions, too loud and so on.
The new player is much more advanced but with a reduced surface. The player handling grows up with the kid: There are several play modes which can be set up by parents. From RFID mode (and loudness) only mode to much more advanced modes. Even the player can be used as BT Box (I used the PCM mixer plugin and the BT audio out goes into the line in of the VS1053 - simple but it works)

I use only the ID of each tag: It's combined with a specific folder on the SD card (just written as txt file on the card, but can also be created by the player itself).
There are hundred of ideas how to handle the RFID tags: Here are only two examples:
Buy a book with a CD and just place the RFID sticker into the book: So the child only has to place once the book in front of the player and can hear and listen to the book simultaneously.
Place RFID stickers on photos and record for each photo an own story. (Maybe also interesting for senior citizen...)